diff --git a/lib/rules_inline/escape.js b/lib/rules_inline/escape.js
index 81201f0..5c68a23 100644
--- a/lib/rules_inline/escape.js
+++ b/lib/rules_inline/escape.js
@@ -1,8 +1,9 @@
 // Proceess escaped chars and hardbreaks
 
-var ESCAPED = '\\!"#$%&\'()*+,./:;<=>?@[]^_`{|}~-'
-                      .split('')
-                      .map(function(ch) { return ch.charCodeAt(0); });
+var ESCAPED = {};
+
+'\\!"#$%&\'()*+,./:;<=>?@[]^_`{|}~-'
+  .split('').forEach(function(ch) { ESCAPED[ch.charCodeAt(0)] = true; });
 
 module.exports = function escape(state) {
   var ch, pos = state.pos, max = state.posMax;
@@ -14,7 +15,7 @@ module.exports = function escape(state) {
   if (pos < max) {
     ch = state.src.charCodeAt(pos);
 
-    if (ESCAPED.indexOf(ch) >= 0) {
+    if (typeof ESCAPED[ch] !== 'undefined') {
       // escape html chars if needed
       if (ch === 0x26/* & */) {
         state.pending += '&amp;';